Trapped self-draining pitot-static tube



June 11,1940. P. KoLLsMAN 21,204,367

TRAPPED SELF-DRAINING PITOT-STATIC TUBE y Filed May 3, 1938 3 Sheets-Sheet 1 xNVENToR 55% KULLEMFIN A 'l ORNEY` June 1l, 1940. v P KQLLSMAN 2,204,367

TRAPPED SELF-DRAWING PI'roT-s'rATIc TUBE Filed Ilay', 1958 3 Sheets-Sheet 2 INVENTOR I Pm. KULLSMHN l f) BY I WASY June 11, 1940. P. KoLLsMAN TRAPPED szLF-DnAINING PITo'r -STATIC TUBE 3 Sheets-Sheet 3 Filed lay 3, 1938 INVENTOR ATTORN Y Patented June 11, 1940 UNITED STATES PATENT OFFICE lPaul Kollsman, New York, N. Y., assignor, by

mesne assignments, to Square D'Company, Detroit, Mich., a corporation of Michigan Application my a, 193s, lseiiai No. 205,765

,8Claim8.

,This invention relates to airplane speed responsive instruments of the Pitot-static tube type, and relates particularly to a Pitot-static tube having means for separating moisture and 6 water from the air in the tube and means for the trapping out of water away from the instrument line.

In the prior art of the construction of Pitotstatic tubes diiiiculty has been encountered, particularly with tubes mounted on seaplanes, from the entry of spray or other aqueous material or water forms into 'the Pitot-tube which tends to block the tube and disable the connected instruments by the presence of plugs of water in the connecting lines which by their weight andthe capillary attraction at the surfaces, produce false pressures upon the indicating instruments; and diiculty is particularly met in instances when freezing temperatures are encountered which tend to solidify any water present in the various portions of the system producing solid plugs which also tend to interfere with the development of correct pressures and with theoperation -of connected instruments.

It has been customary with prior Pitot-static tubes to provide a streamlined shell having therein a Pitot tube or ,dynamic pressure member` opening at the forward tip of the shell, and slots -or perforations in the side of the shell to provide a static pressure value within the shell.

Both the Pitot tube and the static shell interior are connected by tubular duct lines to a pressure sensitive instrument which responds to the pressure differential between the Pitot pressure line and the -static Pressure line, and indicate the in operating order. -During clear, good, flying weather the, readings of the air .Speed indicator 45 of the plane. However, in-'bad flying :weather when the pilotis yingfon instrumen and under the'neces'sity ofesti-mating the distance.

ilown by a dead reckoning? computed from the 50 indicated air speed and elapsed time, it is of iin-'- portance that his air speedindicator orsimilar' instruments be. wl iolly reliable, but itV is under bad/atmospheric conditionsthat the air speed 'indicator and Pitot tubefconibination is most likely. to fau. -such failure is Ausmiuy d ue to oi-v are of interest, butnot vltaltoithe navigation (Cl. 'I3-212) struction of the Pitot tube or of the static shell by frost, ice or water from the spray, or from vthe fog, rain or snow through which the pilot may at the moment be Ming.

In my copending applications, Serial No. 6 135,858 filed April 9, 1937, and Serial No. 195,465 filed March 12, 1938, there is disclosed a Pitotstatic tube construction in -which there is incorporated a controlled heater member adapted to provide sufcient heat to prevent obstruction l0 of the tubes by ice or' snow which may tend to accumulate thereon, 0r therein.

The present invention provides a Pitot-static tube (adapted if desired to be mounted in a socket attached to aplane member high in the 16 plane structure), in which there is incorporated# a baille means for precipitating water particles and means for trapping out in a trapping chamber any iiuid or waterwhich might otherwise accumulate and means for draining it from the zo trapping chamber, thereby preventing passage of the water into the tube lines .leading to the instrument. 'I'his trapping drainage of the uid from the device .prevents waterlock in ythe lin'es any any resulting pressure abnormalities in the g5 lines leading from the Pitotstatic tube to the instrumentand any consequent false readings of the ,-indicator; and permits placing it even within a spray zone and above the responsive instrument.

Thus; an object of .the invention is to drain water from a Pitot-static tube before it passes therethrough far enough to cause pressureirregularities. Another object of the invention is to trap 35 .water from vthe lines of a Pitot-static speed indicator. i j

Still another object oftheinvention is to prevent the deposition of water and ice in a Pitotstatic tube and to drain and trap the water o therefrom at a point near enough the ,entrance of the'tubes to prevent pressure irregularitie and false indications. 4 A further object of the invention is to provide a Pitot-static tube winch may be mounted above u the level of the indicating instrument without causing water to flow from the tube to the indicating instrument. 1 Still another object of the invention is to 'streamline a Pitot-statictube ,device and to in- 5o corporate therein a streamlined iluid trap.

vOther objects and structural details of the invention will be apparent from the following description' when read in connection with the accompanying drawings wherein:

Fig. 1 is a side view, partly in section, of an airplane and Pitot-static tubes and indicators mounted thereon.

Fig. 2 is a side view, in section, of a Pitotstatic tube having a heater and fluid traps incorporated therein.

Fig. 3 is a front view, in elevation, of the embodiment of Fig. 2.

Fig. 4 is a top view, partly in section, of the embodiment of Figs. 2 and 3.

Fig. 5 is a side view in section of an alternative embodiment adapted to a different type of mounting, and

' the opening I2.

Fig. 6 is a front view of the embodiment of Fig. 5.

Referring to the igurcs, a desirable form of the invention which is particularly adapted to the mounting of the Pitot tube upon theupper surface 0I the airplane structure is shown in Figs. 1. 2, 3 and 4. In these figures the Pitotstatic shell member I is attached to a supporting block or socket 2 as shown in- Figs. 2 and 3. The block or socket 2 is adapted to enter a streamlined tube member for support of the Pitotstatic tube a substantial distance away from, or above, the member of the airplane which carries the tube; or as shown in Fig. 1 the member 2 may cooperate with the'member 3 which in turn is attached to the fuselage 4 of the airplane. The shell member I may desirably consist of a forward portion preferably of substantially elliptical cross-section, surrounding the Pitot tube 5 and a heater member 6; and in addition a water trap portion at the top, which is separated from the rest of the shell I by a partition 1. The water trap portion may assume the form of a sharks n, as shown in the drawings, and form an upward extension of the supporting portion including the socket v2. duct 5, which is terminated rearwardly at the partition 1 is terminated forwardly at a partition 8 in the shell member I. Attached to the front surface of the partition 8 is a boss 9 upon which there is mounted a baiiie member III, facing the dynamic duct opening II.` At the bottom of the chamber formed in theforward portion of the shell I by the partition 8 there is provided a small drain opening I2 through which any water precipitated from entering air by the baiile member I0 is allowed to drain.

As shown in Fig. 1 the Pitot tube member 5 extends from the front end of the shell member I to the trap portion, through the partition 1. There is also provided an instrument line or tube I3 which passes through the partition 'I and up- "ward to a point adjacent the top of the trap portion of the shell I. The tube I3 is extended through the support member 2 and thence to the instrument I4, which may be an indicating instrument of the aneroid capsule type, on the instrument board of the plane or may be any other desired instrument of appropriate type.

' Thus any water which is driven into the opening II impinges upon the baille I Il and is mostly precipitated outupon the baille and drips downward to the bottom of the chamber forward of the partition 8 and drains outward through Any residual water, spray or moisture which is not thrown out by the baille III may enter the tube 5, precipitate therein and may be carried backward until the end of the tube Slis reached, whereafter the water falls to the The Pitot tube, or dynamic' positions of the plane, or through the drain opening I5 at the back of the shell I.

Static pressure, slots I6 are also provided in the shell I rearwardly of the partition 8, and preferably rearwardly of the heater; and a static' pressure line I1 is provided leading `fromthe main portion or static pressure chamber of the shell I (into which the slots I6 open) through thesupport member 2 to the instrument I4. A

. drainport I9 may be provided in the static portion sure in the chamber forward of the partition 8 which is transmitted to the trap portion of the shell I over the partition 1 and thence through the tube I3 to the instrument I4. Simultaneously, the slots I6 permit a pressure to be established within the main portion of the shell I which pressure corresponds to the actual air pressure of the flight altitude of the plane at the time. 'I'his pressure is conveyed through the tube I'I -to the static pressure chamber of the indicating instrument, and the pressure differential provided between the tubes I3 and I1 is perceived by the pressure sensitive member and indicated in terms of the speed of the plane, or other ef'- fects obtained as desired.

During take off from the water or during iiying in rain, snow or sleeting conditions the spray or atmospheric water may tend to enter the opening II, and in the absence of preventative means, to enter the forward l end of the tube 5 and to be carried along tothe trap portion of the shell. The speed of the plane causes any water which enters the opening II to pass inwardly in approximately a straight horizontal line with respect to the shell member I and accordingly the vgreater portion of any water entering the openvprecipitates nearly all of the water driven into the opening II but any spray which escapes the baille I0 tends to pass rearwardly through the dynamic pressure duct or Pitot tube 5 to the chamber above `the partition 1. There, however, the absence of an air ow in the trap chamber permits the water to settle out upon the partition 1. This settled-out water drains away either forward through the tube 5 or backward through the outlet I5.

Flying through spray or rain merely tends to cause water to pass into the Pitot tube. However, iiyingthrough snow `may cause 'the depositing of considerable amountsof snow within the tube which may be suiiicient to close the end of the tube. This closure by ice or snow is prevented by the heater i which liberates suiiicient heat adjacent the tube and the forward end of the duct to melt any snow which may be blown into the end of the tube. The melted snow also may drain outwardly through the opening I2, and any which may enter the tube l also is melted therein and `mits a segregation of the trap space without inmay flow forward along the tube or it may be carried backward into the trap portion and settle out on the partition 1. From this position it may still drain forward through the tube 5, or it may drain backward through the outlet l5,

Thus the Pitot tube as well as the static shell are kept free from water, ice and snow and are drained from spray or rain or snow water. Similarly, during sleeting conditions when ice may tend to form in or upon the tube 5 or the shell I, the heater 6 maintains a suiciently high temperature to prevent formation of icefrom such causes as the presence of super-cooled atmospheric moisture.

The above described embodiment of the device of the invention is particularly adapted to mounting upon the upper surface of an airplane structure such as the upper surface of a Vwing or the upper surface of the fuselage, and when s'o mounted it has the outstanding value that it may be situated in a location higher than the level of vthe indicating instrument without danger of the connecting lines becoming water-locked, and without danger of the ow of Water to the indicating instrument. h l

When so mounted, the device has the 'further advantagethat it isvabove the greater portion of the spray thrown by the air blast when a plane is taking off from the surface of the water; and the further advantage that any spray which does enter the Pitot'tube is caught and drained out of the lines before there is any chance for it h' to flow down to the indicating member.

Alternatively, the embodiment of Figs. 5 and 6 may be utilized. 'I'his embodiment is particularly. adapted tomounting uponpthe forward edge of an airplane structure such as the forward edge of a wing or the forward end of the fuselage or upon a strut or other portion of the plane.

As shown in Figs. 5 and 6 this alternative embodiment consists of a shell portion 2| which is streamlined as shown, and attached to a supporting socket member 22 which, as before, may be mounted upon a supporting tube or upon a member 23 andV form a horizontal extension of the horizontal shell portion. A dynamic tube 25 is mounted within the shell 2| and a heater 26 is provided adjacent the tube 25. A protuberant portion of the shell 2| is separated by a partition 21 to form a trap portion and a tube member 33 is provided entering the trap portion through the partition 21 and extending to a point near the top of the trap chamber. 'I'he tube 33 is continued through appropriate tube vlines to the indicating instrument 34. A suitable drain opening 35 at the rear of the trap opening is provided as shown. Static pressure slots 36 are also provided and the static pressure line 3-1 is connected to the static pressure space of the shell 2| by way of a settlingpocket 38. The tube 31 is similarly extended to the indicating instrument 3l. v

A partition 28 similar to the partition 8 of the first embodiment is provided to which there is attached a similar boss 29 and a similar baille plate 30 facing the front opening 3|. A similar drain opening 32 is likewise provided. A further drainport 39 may be provided in the static portion or chamber of the shell.

This embodiment operates in a manner closely similar to the previously described embodiment and the minor differences in operation will be apparent upon inspection of the drawings.

'Ihe streamlining of the shell includes a streamlining of the trap portion and thereby perterference either with the forward progress of the plane or with the accuracy of reading of the indicator, since no troublesome eddies or other disturbances are produced.

Either cf the above described embodiments may, if desired, Vbe mounted upon the end of a tubular strut in a manner closely similar to that of the previous types of Pitot tubes. Either embodiment is, however, particularly adapted to, and preferably mounted upon, a short socket directly attached to a convenient member of the airplane structure; and when so mounted the stresses imposed upon the shell by vibration or other movements given to the Pitot tube produce minimum amounts of stress because of the lower leverage incident to the shorter` supporting member and the shorter radius of gyration.

The invention thus comprises a streamlined shell having therein a dynamic pressure tube,

static pressure slots, a baille and chamber at the.

forward end, water traps and drains for both thereof, and a heater for preventing the formation of ice or obstructions in the tube structure, such that the connected indicator is prevented from giving false indications because of obstructions of the Pitot-static members by ice.

While there are above disclosed but a limited number of embodiments of the deviceof the invention it is possible to provide still other embodiments thereof without departing. from the inventive concept herein disclosed and it is therefore desired that only such limitations be imposed upon the appended claims as are stated therein.

What I claim and desire to protect by United States lLetters Patent is:

1; A Pitot tube comprising a shell having a substantially horizontal tubular portion and a prov'a protuberance extending above said horizontal portion, the horizontal portion being provided with a static pressure opening in the side wall thereofand -forward of said protuberance; a par-v tition separating the space within the protuberance to form a first chamber separate from the remainder of `the space within said shell, said remainder constituting a second chamber; a dynamic pressure duct in said horizontal portion forming a dynamic pressure port at the front end of the horizontal portion and terminating in said first chamber; and pressure ducts leading from the upper portions of said first' and second chambers respectively.

3. A Pitot-static tube comprising a shell having a substantially horizontal tubular portion of Isaid protuberance; a partition separating the 'space within the protuberance to form a first chamber separate from the remainder of the space within said shell, said remainder forming a second chamber; a dynamic pressure duct in said horizontal portion connecting said dynamic pressure opening and said first chamber; a socket member supporting said shell; and pressure ducts leading downward from the upper portions oi said first and second chambers respectively and through said socket member.

4. A Pitot-static tube comprising a shell having a substantially horizontal tubular portion and a protuberance extending above said horizontal portion, the horizontal portion being provided with a static pressure opening in the side wall thereof and forward of said protuberance; a partition separating the space within the protuberance to form a rst chamber separate from the remainder of the space within said shell, said remainder constituting a second chamber; a dynamic pressure duct in said horizontal portion forming a dynamic 4pressure port at the front end of the horizontal portion and terminating in said iirst chamber; a. socket member supporting said shell and forming a substantially vertical downward extension thereof in line with said protuberance; and pressure ducts leading downward and outward of said shell from the upper portions of said first and second chambers respectively and through said socket member.

5. A Pitot-static tube comprising a shell having a substantially horizontal tubular portion anda protuberance extending above said horizontal portion, the horizontal portion being provided with a static pressure opening in the side wall thereof and forward of said protuberance; a partition separating the space within the protuberance to form a first chamberseparate from the remainder of the space within said shell, said remainder constituting a second chamber; a dynamic pressure duct in said horizontal portion forming a dynamic pressure port at the front end of the horizontal portion and terminating in said rst chamber; a socket member supporting said shell and forming a substantially horizontal extension thereof substantially in line with said horizontal portion; and pressure ducts leading downward and outward of said shell from the upper portions of said rst and second chambers respectively and through said socket member.

6. A Pitot-tube comprising a shell having a substantially horizontal tubular portion and a protuberance extending above said horizontal azac-aas? portion; a partition separating the space within the protuberance to form a chamber separate from the remainder of the space within said shell, a drainport being provided connecting the lower portion of said chamber tothe outside of said shell; a dynamic pressure duct in said horizontal portion forming a dynamic pressure port at the front end of the horizontal portion and terminating in said chamber; and a pressure duct leading outward of said shell from the inside of said chamber at a point above said drainport.

7. A Pitot-static tube comprising a shell having a substantially horizontal tubular portion and a protuberance extending above said horizontal portion, the horizontal portion being provided with a static pressure opening in the side wall thereof and forward of said protuberance; a partition separating the space within the protuberance to form a rst chamber separate from the remainder of the space within said shell, said remainder constituting a second chamber, a rst drainport being provided connecting the lower portion of said rst chamber to the outside of said shell, and a second drainport being provided connecting the lower portion of saidsecond chamber to the outside of said shell; a dynamic pressure duct in said horizontal portion forming a dynamic pressure port at the front end of the horizontal portion and terminating inl said first chamber; and pressure ducts leadingl outward of said shell from points in said first and second chambersl respectively above the respective drainports.

8. A Pitot-statlc tube comprising a T-shaped shell having a horizontal portion forming one arm of the T and having a dynamic pressure port' at the front rnd,`a closed protuberance extending substantially vertically abovev said horizontal portion and forming the second arm of the T, and a supporting extension forming the third arm of the T substantiall; aligned'with one of the other arms; a partition separating the space within the prtuberance to form a chamber separate from the remainder of the space within said shell; a dynamic pressure duct in said horizontal portion connecting said port and said chamber;

' and a pressure ductv leading downward from said chamber and outward of said shell through said supporting extension.

v PAUL KOLISMAN. 

